1. Field of the Invention
The present invention relates to a drum head tension control device, and particularly relates to a drum head tension control device that is mounted on a drum to adjust the distance between two drum hoops and the resultant tension on the drum heads.
2. Description of Related Art
With reference to FIG. 4, a drum normally has a cylindrical shell (70), two annular drum hoops (80), two drum heads (81) and a tension control device (90). The cylindrical shell includes two round openings and an outer surface face. The drum hoops (80) are mounted respectively on the two openings and are separated by a distance. The drum heads (81) are mounted respectively in the drum hoops (80), cover the two openings, are made of leather or similar resilient material and emit a tone depending on tension applied to the drum heads (81). The tension control device (90) is mounted between the two drum hoops (80) and controls the tone of the drum heads (81) by controlling the distance between the two drum hoops (80).
With further reference to FIG. 5, a conventional tension control device (90) has a mounting post (91), a sleeve (92), a attachment bolt (93) and two adjustment bolts (94). The mounting post (91) is mounted on the outer surface of the of the cylindrical shell (70) and has a proximal end (not numbered), a distal end (not numbered), a longitudinal hole (911) and a transverse hole (912). The longitudinal hole (911) is defined coaxially through the proximal end into the mounting post (91). The transverse hole (912) is formed diametrically through the mounting post (91) near the distal end and communicates with the longitudinal hole (911). A sleeve (92) is mounted through the transverse hole (912) and has a middle (not numbered), two open ends (not numbered), an internal thread (not numbered) and an attachment hole (not numbered). The internal thread is defined longitudinally in the sleeve (92). The attachment hole is defined through the middle of the sleeve (92). The attachment bolt (93) is screwed into the longitudinal hole (911) in the mounting post (91) and the attachment hole in the sleeve (92) to securely hold the sleeve (92) in the transverse hole (912) of the mounting post (91). The adjustment bolts (94) are mounted respectively through two holes respectively in the drum hoops (80) and are screwed respectively into opposite ends of the sleeve (92). Each attachment bolt (94) has a proximal end (not numbered), a distal end (not numbered) and a flange (941). The flange (941) is formed near the distal end of the attachment bolt (94) and abuts the hole in the drum hoop (80) opposite to the sleeve (92). The proximal ends of the adjustment bolts (94) screw respectively into the ends of the sleeve (92) to adjust the distance between the drum hoops (80) and the tension on the drum heads (81).
However, the holes in the drum hoops are not necessarily aligned with each other. Screwing one end of one of the adjustment bolts (94) into one end of the sleeve (92) will cause the opposite end of the sleeve (92) to misalign with the corresponding hole in the opposite drum hoop (80). Consequently, extending the other adjusting bolt (94) through the hole in the opposite drum hoop (80) and screwing it into the other end of the sleeve (92) may be difficult or impossible. Furthermore, the tension on and tone of the drum head (81) may change when the second adjusting bolt (94) is screwed into the sleeve (92).
Therefore, the invention provides a drum head tension control device to mitigate or obviate the aforementioned problems.